Pressure actuated seal with relief means



Filed Oct. 2, 1952 July 5, 1955 c. R. NEILON 2,712,455

PRESSURE ACTUATED SEAL WITH RELIEF MEANS 3 Sheets-Sheet 1 6 1a 7 21 l 19 f8 20 17 1g 15 i 14 L x Z, 12

%mwz 27M INVENTOR.

July 5, 1955 c. R. NEILON 2,712,455

PRESSURE ACTUATED SEAL WITH RELIEF MEANS Filed Oct. 2, 1952 5 Sheets-Sheet 2 IN V EN TOR.

BY 7751mm jfyz/ZZ July 5, 1955 c. R. NEILON PRESSURE ACTUATED SEAL WITH RELIEF MEANS 3 Sheets-Sheet (5 Filed Oct. 2, 1952 INVENTOR. BY fi/wu/ 7/1 W United States Patent PRESSURE ACTUATED SEAL WITH RELIEF MEANS Claude R. Neilon, Houston, Tex., assignor to The National Supply Company, Pittsburgh, Pa., a corporation .of Pennsylvania Application October 2, 1952, Serial No. 312,822

3 Claims. (Cl. 285-22) This invention relates to joint sealing means for wellheads and an object of the invention is to provide in a wellhead a novel type of slip assembly which may be assembled around the pipe and lowered through the blowout preventers and gate valve to seat in the wellhead casing and which will form not only pipe supporting means but sealing means between the casing, the assembly, and the inner pipe.

It is a prime object of the present invention to provide automatic sealing means carried by the slip assembly which will seal the annulus between the inner pipe and the outer casing so that a seal is effected, exclusive of the seal carried by the blowout preventer assembly mounted on the upper flange. Since it is often necessary to remove the blowout preventers and upper gate valve in order to mount the Christmas tree assembly on the well, it becomes necessary to have some sort of sealing means which will prevent any blowout of gas while the change is being eifected. To accomplish this, it is necessary to have a seal located below the removable preventer equipment elements. The seal means are therefore carried by the slip assembly which remains in the wellhead casing during this change.

A further object of this invention is to provide compensating means to control the pressure within the sealing media. This compensating means is used to insure proper seating of the slip assembly in the wellhead without having such a sealing pressure on the pipe so as to collapse it.

A further object of this invention is to provide a means to control the radial (horizontal) movement of the slip segments which will permit the slip assembly to be readily and rapidly removed from the preventer bore in the event a restriction such as a partially closed preventer ram or a collar on the suspended string should be encountered while the slip assembly is being lowered into place through said preventer equipment.

A still further object of this invention is to provide temporary locking means for the slip assembly so that the slip assembly may be mounted at a designated point on the pipe and then be lowered with the pipe down through the blowout preventers and gate valve to seat in the wellhead casing.

Other objects and advantages will become apparent from the following specification taken in connection with the accompanying drawings which describe the more convenient and flexible form of the invention in which the spider is split on its diameter. Obviously, a similar structure could be provided using a solid spider. In the drawings: I

Fig. 1 is a side elevation of the complete head shown in vertical section.

Fig, 2 is a perspective view of the slip assembly shown in its open or split position, wherein one of the slips is fragmentary.

Fig. 3 is a top view of the seal element.

Fig. 4 is an enlarged fragmentary vertical section view taken on line 44 of Fig. 2 showing the locking means.

ice

Fig. 5 is an enlarged fragmentary view of Fig. l with the slip element in its uppermost position.

Fig. 6 is a vertical section taken on line 6-6 of Fig. 3.

Referring now, more particularly, to the drawings wherein like numerals of. reefrence designate the same part in each of the figures, the numeral 1 designates the type of casing head which is attached to the upper end of the well casing 2, and which is provided with an internal annular seat 3 which preferably tapers downwardly and inwardly, and said head may also be provided with an external flange 4 at its upper end for attachment of the gate valve and blowout preventers (not shown).

The casing hanger assembly is designated generally at 5. The casing hanger assembly is composed, generally, of a spider 6 split on its diameter, each half of said spider being provided on each end thereof with an offset locking hinge 7, so that a permanently installed hinge pin 8 may be provided on one side and a loose locking pin 9 may be provided on the other side. The outside periphery 16 of this spider is such that it may be passed through the standard full opening blowout preventers, and its lower section 11 is tapered to match the tapered bore 3 of the casing head body. The interior of this spider has a similar tapered bore 12 of a smaller inner diameter to receive a four segment slip assembly 13 which is retained within the spider by means of shoulder screws 1.4 installed through vertical slots 15 in the Wall of the spider. The spider also has another tapered bore 16 at its upper end extending from the previously mentioned inner diameter but reversed in direction. The outer surfaces of the slip elements are provided with long, tapered surfaces 17 which transmit the pipeload to the spider and, with a short tapered section 18 at their upper end, which taper is inverted to the load bearing taper 17. Each of the four slip segments are provided with drilled wire handle boxes 19, located above the shoulder screw 14. Ports 20 to accept these Wire handle boxes, as well as the wire hantile 21 itself, are provided in the wall of the spider and a protruding ledge 22 integral with the spider is located above the wire handle box so that when the slip segments are lifted by the wire handles the slip segment is raised upward and outward away from the suspended pipe string as shown in Fig. 5 and is aligned in this position by virtue of the inverted tapered surface. Thus a means is provided which permits the assembly to be raised upward along the inner pipe (as is sometimes necessary in practice) without danger of the slip teeth or wickets digging into and locking the assembly on said pipe within the preventer bore.

Each of the slip segments has in one vertical end face a pointed dowel 23 and a corresponding but oversized hole 24 in the opposite face. Two of the slip segments are assembled by means of the shoulder cap screws 14 into each half of the split spider, and one end of a wire rope handle is attached to each of these slip segments.

Therefore, when the spider halves are hinged open, and the slip segments are raised by means of the wire handles, the dowels, which mate with the corresponding holes in the adjacent slip segment, control relative vertical movement of both of the slip segments within each half of the spider, and when the spider is in its closed position, the dowels of each segment will control the relative vertical nidvemeht of all four slip segments causing them to move together vertically as an integral unit.

Two tapped holes 25 are placed in the upper section of the' split spider, one in each half as shown in Fig. 4. These holes are tapped at an angle to the vertical wall of the slip segment so that when they are equipped with a set screw 26 and the spider halves are fastened around the pipe, these set screws can be made to force the in dividual slip elements into gripping engagement with the pipe to be suspended. When, however, an additional load is taken by the slip segment, as when the pipe is released during the slacking off operation, the slip element will pull tighter and, consequentially, pull away from the set screws used in the preliminary locking or gripping position.

A molded resilient packing element 27 is positioned in the lower end of each split spider half. This molded element is made up of two circular rings 28 and 29 approximately rectangular in cross section; the inner ring 28 being positioned below the upper ring 29 with ten radially disposed members 30 interconnecting them, although a different number may be used. It is split on its diameter through opposite radial connecting members and in the same plane as that in which the split of the spider is located. Annular grooves 31 and 32 and radial ports 33 are provided in the spider to receive this packing. The four radially disposed interconnecting members in each of the halves of the seal are cut, prior to installation in the spider, at a point between the inner and outer ci-rcular rings. upper circular ring is tapered and protrudes beyond the tapered surface 11 of the spider so that this protrusion contacts the tapered bowl 3 of the casing head body and is compressed when the pipe weight is transferred through the slip and spider to the wellhead body. The resulting compression in the outer ring 29 of the packing seal is transmitted through the radially disposed interconnecting members 30 to the inner circular ring 28 and results in a uniform packing compression throughout the seal. Thus an effective seal is obtained at the outside diameter of the spider and at the outside diameter of the suspended string, as well as across the diametric split 35 at the juncture of the two spider halves:

The respective physical dimensions of this molded resilient packing element must be such that an effective seal will be obtained around a pipe of any diameter within the range of diameters permissible for a given nominal pipe size produced under standard rolling mill tolerances for tubular materials and such that an effective seal will be obtained with the weight due to a suspended string of the minimum length which occurs in practice. Therefore, the volume of the resilient packing material contained within that portion of the molded packing which protrudes beyond the tapered surface of the spider is in excess of that required to seal around a pipe of the minimum diameter of a given nominal size, although in practice, the hanger will frequently be used with pipe of the maximum diameter of a given nominal size. The length of the outer circular ring in contact with the tapered surface 3 of the casing head of this molded resilient packing is established so as to provide the desired packing compression with a suspended string of a length'less than that which occurs in actual practice, although the hanger will always be used with longer suspended pipe strings. The excess volume of the packingmaterial and the excess packing pressure thus obtained will be controlled automatically; for below the inner ring of the packing seal, an annular groove 36 is located in the split spider leaving a relatively thin flange of metal 37, the

thickness of which is proportioned so that, when a pre-;

determined compressive stress due to the suspended casing load is attained in the resilient packing material 27, this flange will be deflected, thereby relieving any excess packing compression without danger of collapsing or crushing the suspended pipe. This predetermined load relieving means permits the sealed slip assembly to be used with the complete range of pipe diameters encountered in practice and assures a positive seal regardless of the length of the suspended string. Since the stress will not be relieved until a predetermined stress is attained, the seal will grip tightly upon a pipe of large or small diameter within the minimum tolerances allowed. At the same time, this load relieving stress flange 37 provides a means whereby the hanger assembly is guaranteed to properly seat in the head since the compressive load can be re- The outside surface 34 of the outer and lieved until the seal is compressed a suflicientamountto permit the tapered outer surface 11 of the assembly to engage the tapered surface 3 of the casing head. Obviously, a comparable packing load relieving means can be provided in the OD of the spider and such means can be used in'conjunction with or as an alternate to the means just described.

The operation of the unit is as follows. The unit is wrapped and fastened around the string to be suspended and locked into position by means of the locking set screws at the rotary table elevation so that it can be lowered with the casing string to be suspended down through the preventers to come to rest in the bowl of the casing head body. The unit may also be placed around the inner string at'an elevation just above the rotary table, then lowered down through the rotary table and the blowout preventer equipment by means of soft lines to come to rest in the tapered bowl of the casing head body. In the latter instance, it is anticipated that the inner or suspended string, would be cemented on the bottom prior to running the hanger. In the former instance, the hanger would be fastened to the inner string and lowered to its seat on the casing prior to cementing the inner string on the bottom. When the string is released and lowered away, the split assembly would grip and bite into the pipe.- Through the tapered surfaces, the slip would transfer the load to the spider assembly which, in turn, would transfer the load through its tapered surfaces to the casing head. The force exerted by the casing head upon the sealing ring would transmit the load to the radial members giving an equal compression sealing between the spider and the casing head and between the spider andthe inner pipe. An overload cannot be produced in the packing material because the thin flange element is able to bend downward relieving the excess stress in the seal, permitting the spider to seat in the casing without danger of collapsing the inner pipe.

The drawings and specification are merely illustrative and are not limiting except to the extent of the appended claims.

What I claim is:

1. In a Well head having a bowl member formed with an opening therethrough having a downwardly and inwardly tapered inner surface to receive a pipe suspend ing and sealing means, a shell member having slip elements slidable therein for engagement with the outer surface of a suspended pipe string and an outer surface mating with the tapered surface of said opening, incompressible resilient'sealing means mounted in said shell member comprising, an outer annular sealing ring mounted in a groove in the outersurface of said shell member and normally extending therefrom, an inner annular sealing ring mounted in a groove in the inner surface of said shell member and normally extending adjacent to said inner surface, said shell member having a plurality of openings connecting said inner and outer grooves, a plurality of connecting ribs in said connecting openings joining said inner and outer sealing rings for transmitting compressive forces from said outer ring to said inner ring, said inner groove having means comprising a relatively thin wall portion yieldable under pres sure of said sealing means to limit the maximum force exerted by said 'inner'ring against said suspended pipe string to less than the collapsing strength of the pipe, said sealing means substantially filling said mourning grooves and connecting openings.

2. In a well head having a bowl member formed with an opening therethrough having a downwardlyand inwardly tapered inner surface to receiveapipe suspending and sealing means, a shell member having slip elements slidable therein for engagement with the outer surface of a suspended pipe string and an outer surface mating with the tapered surface of said opening, incompressible.resilient sealing means mounted in said shell member comprising, an outer annular sealing ring mounted in a groove in the outer surface of said shell member and normally extending therefrom, an inner annular sealing ring mounted in a groove in the inner surface of said shell member and normally extending adjacent to said inner surface, said shell member having :1 plurality of openings connecting said inner and outer grooves, a plurality of connecting ribs in said connecting openings joining said inner and outer sealing rings for transmitting compressive forces from said outer ring to said inner ring, and means comprising a relatively th n wall portion adjacent one of said grooves yieldable under pressure of said sealing means to limit the maximum force exerted by said inner ring against said suspended pipe string to less than the collapsing strength of the pipe, said sealing means substantially filling said mounting grooves and connecting openings.

3. In a Well head having a bowl member formed with an opening therethrough having a downwardly and inwardly tapered inner surface to receive a pipe suspending and sealing means, a shell member having slip elements slidable therein for engagement with the outer surface of a suspended pipe string and an outer surface mating with the tapered surface of said opening, incompressible resilient sealing means mounted in said shell member comprising, an outer annular sealing ring mounted in a groove in the outer surface of said shell member and normally extending thterefrorn, an inner annular sealing ring mounted in a groove in the inner surface of said shell member and normally extending adjacent to said inner surface, said shell member having a plurality of openings connecting said inner and outer grooves, a plurality of connecting ribs in said connecting openings joining said inner and outer sealing rings for transmitting compressive forces from said outer ring to said inner ring, means comprising a yieldable portion of said shell member adjacent said sealing means yieldable under pressure of said sealing means to limit the maximum force exerted by said inner ring against said sus pended pipe string to less than the collapsing strength of the pipe, said sealing means substantially filling said mounting grooves and connecting openings.

References Cited in the file of this patent UNITED STATES PATENTS 2,131,400 Johnson et a1 Sept. 27, 1938 2,312,487 Roach et al. Mar. 2, 1943 2,481,732 Edwards Sept. 13, 1949 2,493,556 Stone Jan. 3, 1950 2,496,190 Works Jan. 31, 1950 2,553,838 Allen et al. May 22, 1951 2,683,047 Allen July 6, 1954 

